1. Field
The disclosure relates to a medium access control (MAC) device and method for optical packet-switched metro wavelength division multiplexing (WDM) slotted-ring networks, which are used for providing quality of service (QoS) guarantees for isochronous traffic.
2. Related Art
Metro networks mainly include synchronous optical network/synchronous digital hierarchy (SONET/SDH) ring networks. Due to the advantages of simple network architecture, easy implementation using add-drop multiplexers (ADMs), and capability of providing high-speed protection switching, ring networks can meet high survivability requirements, and are thus always the main network architecture for metro networks. A SONET/SDH network is circuit switched based in nature, and is quite advantageous for constant bit rate (CBR) applications such as voice service. However, for variable bit rate (VBR) applications such as data service, network resources are wasted.
In recent years, the flow size of the data service has exceeded the voice service, and the difference becomes increasingly larger. Therefore, it is necessary to design a MAC technology for optical packet-switched metro WDM slotted-ring networks that is suitable for burst traffic, so as to satisfy fair bandwidth allocation, and achieve QoS guarantees for isochronous traffic.
M. Marsan, A. Bianco, E. Leonardi, A. Morabito, and F. Neri et al., in “All-Optical WDM Multi-Rings with Differentiated QoS”, IEEE Communications Magazine, vol. 37, no. 2, February 1999, pp. 58-66, disclosed a synchronous round robin with reservation (SR3) mechanism for establishing a connection with a reserved bandwidth, in which a call admission control (CAC) mechanism implements connection admission management using token-like signals by broadcast. In this method, 2 to 3 ring time is required for establishing a connection, and the number N of nodes and the number W of data channels in the ring network are required to be equal, so that the system is not flexible.
In addition, K. Bengi and H. Van As et al., in “Efficient QoS Support in a Slotted Multihop WDM Metro Ring”, IEEE Journal on Selected Areas in Communications, vol. 20, no. 1, January 2002, pp. 216-227, proposed another similar technology, except that this system allows the number N of nodes to be larger than the number W of data channels in the ring network. This system architecture is more flexible as compared with the above technology, but still requires a long period of time for establishing a connection.
In the above two conventional technologies, the former one is to provide a reserved bandwidth for a certain pair of source-destination nodes, the latter one is to provide a reserved bandwidth for a certain destination node, and an address of the reserved bandwidth is fixed at a certain wavelength of a specific slot, instead of being flexibly allocated according to the requirements.
H. Leligou, J. Angelopoulos, C. Linardakis, and A. Stavdas et al., in “A MAC protocol for efficient multiplexing QoS-sensitive and best-effort traffic in dynamically configurable WDM rings”, Journal of Computer Networks, vol. 44, no. 3, February 2004, pp. 305-317, proposed a centralized CAC mechanism for establishing a connection with a reserved bandwidth. In this conventional technology, bandwidth will be marked whenever high priority data cannot be sent out, which compresses the bandwidth of other low priority data.